parse_date: raise ParseError instead of leaking IndexError/ValueError

[simpleqt]

Summary

parse_date indexes the numbers extracted from the input string by the positions of y/m/d in the locale's date pattern, but never checks how many numbers were actually found. Input with fewer than three numbers — including month-name dates like the locale's own medium/long formats — crashes with a bare IndexError:

>>> from babel.dates import parse_date
>>> parse_date('Jan 3, 2026', locale='en_US')     # en_US medium format
IndexError: list index out of range
>>> parse_date('1. Januar 2026', locale='de_DE')
IndexError: list index out of range

Out-of-range fields likewise leak datetime.date()'s ValueError, which except ParseError handlers do not catch:

>>> parse_date('01.32.2026', locale='de_DE')
ValueError: day 32 must be in range 1..31 for month 1 in year 2026

This PR raises ParseError for both cases, matching the existing No numbers were found in input behavior. parse_time already guards its indexing (len(numbers) > 1 / > 2), so this brings the two parsers in line. (Month-name support remains a separate, already-acknowledged FIXME; this only fixes the error contract.)

Verification

• Red/green: test_parse_date_raises_parse_error_instead_of_index_error and test_parse_date_raises_parse_error_on_out_of_range_values fail on master (IndexError / ValueError raised instead of ParseError) and pass with this change.
• pytest tests/test_dates.py: 1193 passed with this change vs 1191 on master against the same environment (5 pre-existing failures identical on master — CLDR data drift in my local setup; no regressions).
• ruff check clean.

AI Disclosure

This PR was prepared with the assistance of an AI coding agent.

• Tool(s): ZCode (GLM-based coding agent)
• Used for: discovering the exception leaks via a locale matrix sweep of parse_date, implementing the guards, and running the red/green and baseline verification described above.

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